First cut of pulling out the relevant parts of my original game to make a little framework.

scripts/pixelize.ps1

@@ -0,0 +1,16 @@
+Param (
+    [string]$InFile,
+    [string]$OutFile,
+    [string]$Colors=16,
+    [string]$Size="256x256",
+    [string]$Pixel="7"
+    )
+
+cp $InFile temp.png
+# magick temp.png -colors $Colors -quantize sRGB -dither FloydSteinberg color.png
+
+magick temp.png -posterize $Colors -quantize sRGB -dither FloydSteinberg poster.png
+
+bash ./scripts/magick/pixelize -s $Pixel -m 2 poster.png pixels.png
+
+magick.exe pixels.png -interpolate nearest -interpolative-resize $Size $OutFile